Segmented pipe couplings are well-known in the art. Those couplings employ two or more coupling segments having retaining keys that are received in grooves in the adjacent ends of pipes, the coupling segments embracing the pipes in encircling relation, and being secured one to the other in end-to-end relation by traction bolts.
Segmented pipe couplings providing a lateral outlet also are well-known in the art, for example, from St. Clair et al., U.S. Pat. No. 3,362,730, one or each of the coupling segments providing a lateral outlet for the connection of a lateral outlet pipe. Either a single one of the coupling segments can be provided with the lateral outlet to provide a T-coupling, or, in the alternative, both or each of the coupling segments can be provided with a lateral outlet to provide a double T-coupling, the possibility being that there are more than two coupling segments each of which is provided with a lateral outlet, for example, four such coupling segments providing an X-coupling.
Such couplings incorporate a sealing gasket that spans the adjacent ends of the pipes, and provides the required sealing of the coupling.
The prior art teachings are of a circular recess surrounding the lateral outlet opening in the coupling segment, in which a circular boss provided on the sealing gasket is received. The circular boss was found to be essential, in that the opening extending radially of the sealing gasket provided a source of leakage behind the sealing gasket, and also a source of structural weakness in the sealing gasket, that, under operational conditions, could cause the radially inwards collapse of the sealing gasket away from the containing coupling segment.
However, the provision of a radially extending boss on the sealing gasket, of necessity required the molding of the cylindrical boss at the time the sealing gasket itself was molded. Further, if more than one lateral outlet was to be provided by the coupling, then, a corresponding sealing gasket having two or more cylindrical bosses had to be provided, in order to provide the required sealing at the respective lateral outlets.
Thus, the sealing gasket for a specific form of lateral outlet coupling differed from a sealing gasket to be employed with a different form of lateral outlet coupling. This, in turn, involved the provision of a multiplicity of molding dies of different configuration, which in turn required separate warehousing, inventory control, and related complexities.
Clearly, it would be a major advantage if a gasket structure could be provided that is standard to any form of lateral outlet, regardless of the number of lateral outlets to be provided. So doing would very significantly reduce the manufacturing costs of such gaskets, the number of molds required for the production of a sealing gasket for a specific outside diameter of pipe then being reduced to one, as opposed to the requirement for a multiplicity of molding dies in order to produce sealing gaskets of the same nominal diameter, but which were intended for use with lateral outlet couplings of differing configuration, which include variants of T-couplings, Y-couplings, X-couplings, and, couplings having lateral outlets located in other configurations, for example, a single gasket segment providing two or more lateral outlets.
As will be apparent from the proceeding discussion, a great variety of molding dies have to be provided to meet specific requirements of lateral outlet segmented pipe couplings. As also will be appreciated, considerable savings in manufacturing costs can be effected in the event that a single sealing gasket of any particular standard size can be employed to provide any number of lateral outlets in any desired configuration of angular displacement, without the necessity of having to provide a specific mold for each specific organization of lateral outlets of a specific lateral outlet segmented pipe coupling.
So doing would enormously reduce the costs of molding dies, would greatly simplify warehousing control, and would greatly reduce the storage warehousing requirements.
Known forms of lateral outlet segmented pipe couplings require an asymmetrical sealing gasket having a radially extending protuberance that extends into the lateral outlet in sealing relation with the interior of the coupling segment providing the lateral outlet, the provision of the radial protuberance constituting an additional complication in the molding of the sealing gasket, with a consequential increase in the cost thereof, and, additionally, requiring the warehousing and inventory control of additional non-standard gaskets.
The reason for providing the radial protuberance on the sealing gasket is, more particularly, required in order to control seepage behind the sealing gasket and lifting of the sealing gasket away from the containing gasket segment, any such lifting action acting further to increase seepage and leakage in a direction circumferentially of the sealing gasket and of the containing segmented pipe coupling.
St. Clair et al. U.S. Pat. No 3,362,730, then requires lugs to be provided on the gasket exterior that are clamped between the adjacent end faces of the respective coupling segments, this further complicating the gasket molding procedures, and increasing the costs thereof.
Shohan U.S. Pat. No. 2,874,979 teaches an irrigation coupling having a lateral outlet, and which incorporates a sealing gasket of C-shaped cross-sections, the sealing gasket being devoid of any radial protrusion for reception within the laterally extending outlet, and aperture being provided in the axially extending outer wall of the sealing gasket, in order to permit fluid to flow between the respective pipes and the lateral outlet.
This, however, requires that the outlet aperture be provided in the relatively weak axially extending outer wall of the sealing gasket, the consequence then being that, when under pressure, the axially extending outer-wall of the sealing gasket can collapse away from the containing coupling, thus permitting seepage circumferentially of the gasket exterior and out of the coupling.
While this is of little consequence in an irrigation system, it is of particular consequence in the event that the pipe line is intended to convey flammable or noxious fluids, or, in the case of a fire extinguishing system, which must be left under full pressure for extended periods of time and be entirely free of leakage and dripping.
When tightening down a segmented pipe coupling as is known in the art, the legs of the sealing gasket are placed under appreciable compression, and, unless prevented from so doing, will attempt to rotate away from the radially extending inner walls of the coupling segments.
This tendency in a conventional sealing gasket is resisted by the axially extending radially outer wall of the sealing gasket, which itself is placed under axial compression in addition to the radial compression produced by tightening down of the coupling segments.
If, however, a radially extending aperture is provided through the axially extending radially outer wall of the sealing gasket, then, as was recognized by St. Clair in U.S. Pat. No. 3,362,730, some form of reinforcement must be provided at that location, which is accomplished by St. Clair in providing a tubular protuberance on the outer surface of the gasket. This, however, carries with it the requirement that the coupling segment must be correspondingly formed to accommodate the radially extending protuberance, this in turn resulting in added weight in the coupling segment, increased complexity in forming the coupling segment, and consequentially an increase in cost of the coupling segment, all of which considerations are of significance in the fabrication of an extensive pipe line assembly.
In the absence of some reinforcement in the location of the aperture in the axially extending outer wall of the sealing gasket, the sealing gasket can, at that location, move radially inwardly of the pipe coupling, this in turn presenting a channel through which fluid can seep in directions circumferentially within the coupling segments, and also axially within the coupling segments, with seepage occurring at the keys and at the adjacent bolting faces of the coupling segments.